The present invention relates to a method for examining a value document while employing a digital image of the value document which comprises pixels, and means for carrying out said method.
Value documents are understood here to be sheet-shaped objects that represent for example a monetary value and hence should not be manufacturable arbitrarily by unauthorized persons. They hence have features that are not simple to manufacture, in particular to copy, whose presence is an indication of authenticity, i.e. manufacture by an authorized body. Important examples of such value documents are coupons, vouchers, checks and in particular bank notes.
Such value documents are frequently to be checked as to whether they have pre-specified features or also defects. For checking the value documents by machine, value-document processing apparatuses are used. Such value-document processing apparatuses typically have optical sensors by means of which images of the value documents are captured. Said images can then be employed for checking whether the value document has certain features or also defects.
Due to the high resolution of modern optical sensors and the high processing speed of modern value-document processing apparatuses, it is important to be able to carry out the stated checks as quickly and efficiently as possible. This applies in particular to checks of defects whose form and extension are unknown prior to the check.